Holder for sheet-metal sample



June 6, 1961 R. v. MIZIA EIAL 2,937,460

HdLDER FOR SHEET-METAL SAMPLE Filed Oct. 21, 1958 INVENTORS ROSE l. M/Z/A and KENNETH R NALLENWEG" Attorney United States Patent Ofifice Patented June 6, 1951 This invention relates to an improved holder for sheet metal samples undergoing chemical analysis.

Our device is especially useful for holding a tinplate sample while the tin coating is stripped to determine its weight by the so-called Bendix method described in Bendix Patent No. 2,455,726 or the improvement thereon described in Robertson Patent No. 2,716,596. According to this method, a standard size tinplate sample is magnetically suspended from its edge in a solution which dissolves the tin coating on application of an electric current. The weight of tin per unit area then is determined by chemical analysis of the solution. The stripping apparatus described in these patents is satisfactory for samples whose two sides bear coatings of the same weight, but less so for samples whose sides are coated difierentially and require individual analysis on one or both sides. The usual practice has been to mask such samples on one side with plasticized paper or the like while stripping the tin coating from the other side. We have observed this practice leads to inaccurate results, since the masking does not always adhere tightly and sometimes the solution leaks under it. Nevertheless it is apparent our invention has other application where similar problems are encountered.

An object of our invention is to provide an improved holder for a sample, only one side of which is exposed to a solution, which holder effectively prevents the solution from contacting the other side.

A more specific object is to provide an improved holder which employs vacuum means to support a sample in a solution and effectively covers one side of the sample to prevent the solution from contacting it.

In accomplishing these and other objects of the invention, we have provided improved details of structure, a preferred form of which is shown in the accompanying drawing, in which:

FIGURE 1 is a front elevational view of an apparatus for stripping tinplate samples equipped with our sample holder, but omitting the sample and the beaker which contains the solution;

FIGURE 2 is a vertical section through the holder on line IIH of FIGURE 1;

FIGURE 3 is a front elevational view similar to FIG- URE l, but with the beaker and solution in place.

FIGURES 1 and 2 show an apparatus for stripping tinplate samples for analysis, which apparatus includes a panel of rigid insulating material preferably hinged to an upright support 12, and a bracket 13 and shelf 14 of similar material projecting from the front of the panel. Preferably a clip 15 is pivoted to one of the hinges and adapted to engage the panel to hold it in a fixed position While the coating material is stripped from a sample. As in the Bendix and Robertson apparatus, bracket 13 supports a porous tube 16 adapted to contain dilute hydrochloric acid. A copper cathode 17 depends from the upper portion of the panel into the liquid in the tube.

The sample holder of our invention includes a plate 18 of hard rubber or the equivalent pivoted to and depending from another bracket 19 fixed to the front of the panel. Plate 18 contains a vertical passage or bore 20, the upper portion of which receives a closely fitting copper tube 21. An electrode 22 is fixed within said tube in electrical contact therewith and extends to the lower portion of bore 20, where it is in electrical contact with a compression spring 23. Opposite the lower end of bore 20, the plate contains a horizontal passage 24 through which spring 23 extends beyond the outer face of the plate. An annular gasket 25 of soft rubber or the equivalent is fixed to the outer face of the plate and this gasket encircles passage 24. Preferably the plate also contains oblique passages 26 which communicate between its outer face within the central opening of the gasket and its vertical bore. A flexible hose 27 is fitted over the upper portion of the tube 21 and extends to a conventional aspirator, not shown. When it is desired to mount a sheet metal sample S on the holder, plate 18 is pivoted to a position flat against panel 10 and the sample placed over the gasket 25. The aspirator creates a partial vacuum beneath the sample and thus holds it tightly against the gasket and in electrical contact with the end of spring 23. The sample is of a predetermined diameter less than the outside diameter of the gasket.

After a sample 5 has been mounted in this fashion, plate 18 is swung to a position at right angles to panel 10. A container 28, commonly a glass beaker, is placed on shelf 14 and receives both the lower portions of both porous tube 16 and the plate 18. An appropriate solution, such as iodine and potassium iodide in dilute hydrochloric acid described in the Bendix patent, is introduced to the beaker to a level fully submerging the sample. Electric leads 29 and 30 are connected to the cathode 17 and tube 21 respectively and to a suitable D.-C. source, thus making the sample an anode as in the aforementioned patents. The tin coating on the exposed face of the sample dissolves, while the gasket seals the opposite face from contact with the solution in the beaker and thus prevents any dissolution. Since we are interested in stripping the coating from only one face of the sample, We use only a single cathode and porous tube, as distinguished from the apparatus shown in the patents. After the sample has been exposed for the proper length of time, the beaker is removed and the vacuum broken to release the sample. Preferably the hose 27 contains a normally closed outlet 31 which can be opened to break the vacuum. The solution remaining in the beaker is analyzed to determine the weight of tin stripped from the exposed face of the sample as in the patents. A similar procedure can be followed to determine the weight of tin on the other side of the tinplate.

From the foregoing description, it is seen our invention affords a simple holder which positively protects one face of a sheet metal sample from contact with a stripping solution, while exposing the other face. The holder simplifies mounting the sample for such stripping since it eliminates any need for masking with adhesives, yet furnishes a superior seal.

While we have shown and described only a single embodiment of the invention, it is apparent that modifications may arise. Therefore, we do not wish to be limited to the disclosure set forth but only by the scope of the appended claim.

We claim:

In an apparatus for stripping a tin coating from a surface of a tinplate sample, which apparatus includes a panel of rigid insulating material, a shelf projecting from said panel, a container for stripping solution supported on said shelf, a bracket projecting from said panel above said shelf, a porous tube supported on said bracket and extending into said container, and a cathode supported on said panel and extending into said tube, the combination therewith of a holder for the sample comprising a rigid plate of insulating material pivotally supported on said panel and extending into said container, a gasket fixed to a face of said plate and having a central opening, said plate having a vertical bore and a horizontal passage communicating between said bore and the opening in said gasket, a spring housed in said passage, an electrically conductive tube fitted into said bore and extending above said plate, means electrically connecting said last named tube and said spring, and means connected to said last named tube for applying a partial vacuum to said bore and passage for holding the sample on said gasket with one face of the sample exposed throughout its area and the other face sealed against the gasket and in electric contact with said spring thus making the sample an anode, said gasket protecting the latter face from contact with the stripping solution throughout its area.

References Cited in the file of this patent UNITED STATES PATENTS 838,346 Livingston et al Dec. 11, 1906 2,455,726 Bendix Dec. 7, 1948 2,716,596 Robertson Aug. 30, 1955 OTHER REFERENCES Ser. No. 290,026, Weiner (A.P.C.), published July 13, 1943. 

